In general, an electrophotographic photosensitive member is used in an electrophotographic process including a charging step, an exposing step, a developing step, a transferring step, a cleaning step, and the like. In such an electrophotographic process, an electrostatic latent image formed on the surface of an electrophotographic photosensitive member is developed with a toner contained in a developing unit to thereby form a toner image on the surface of the electrophotographic photosensitive member. The toner image is then transferred from the surface of the electrophotographic photosensitive member to a transfer material with a transferring unit. However, even after the toner image is transferred to the transfer material, part of the toner often remains on the surface of the electrophotographic photosensitive member. Hereafter, such a toner remaining after the transferring step is also referred to as “untransferred toner”. In a general electrophotographic process, such an untransferred toner is removed from the surface of an electrophotographic photosensitive member with a cleaning unit. Specifically, an untransferred toner is removed by, for example, a method of bringing a cleaning blade into contact with an electrophotographic photosensitive member and scraping off an untransferred toner from the electrophotographic photosensitive member, a method of using a fur brush, or a combination of these methods. At present, in view of ease of cleaning and cleaning performance, the method of using a cleaning blade is widely employed. As for such a cleaning blade, a cleaning blade composed of an elastic body such as urethane rubber is widely used.
As for an electrophotographic photosensitive member, in view of low cost, high productivity, and the like, an organic electrophotographic photosensitive member is commonly used at present that includes a support and a photosensitive layer (organic photosensitive layer) composed of an organic material serving as a photoconductive substance (a charge generation substance or a charge transport substance), the photosensitive layer being formed on the support. As for such a photosensitive layer (organic photosensitive layer), a multilayer photosensitive layer is mainly used in which a charge generation layer containing a charge generation substance and a charge transport layer containing a charge transport substance are stacked. Such a multilayer photosensitive layer is advantageous in that high sensitivity can be achieved, various material designs are allowed, and the like.
The uppermost layer of an electrophotographic photosensitive member (hereafter, referred to as “surface layer”) has been actively improved for the purpose of enhancing the durability of an electrophotographic photosensitive member or suppressing degradation of image quality. For example, to enhance the strength of such a surface layer, techniques have been studied such as improvement of resins (binder resins) for the surface layer and addition of filler or the like to the surface layer.
However, it is known that an increase in the strength of a surface layer makes it difficult to sufficiently remove charge products (corona products) on the surface of an electrophotographic photosensitive member, which tends to result in image deletion.
To deal with this problem, Patent Citation 1 discloses a technique of removing such charge products from the surface of an electrophotographic photosensitive member in which a toner containing relatively large inorganic fine particles as an external additive is used and the surface of the electrophotographic photosensitive member is polished with the inorganic fine particles.
Patent Citation 2 discloses a technique of processing the surface of an electrophotographic photosensitive member with a stamper having well-shaped depressed portions. Patent Citations 3 to 6 disclose techniques of roughening the surface of an electrophotographic photosensitive member.
As disclosed in Patent Citation 1, a technique of removing charge products adhering to the surface of an electrophotographic photosensitive member is known in which a toner containing relatively large inorganic fine particles as an external additive is used. Specifically, the size of such inorganic fine particles needs to be within the range of 0.1 μm to 1.5 μm.
However, when an identical format is printed many times, for example, vertical lines are continuously printed in a large quantity of sheets, a toner is fed only to specific portions of the surface of an electrophotographic photosensitive member in a concentrated manner. Thus, relatively large inorganic fine particles contained in the toner as an external additive are also fed only to the specific portions of the surface of the electrophotographic photosensitive member in a concentrated manner. As a result, the inorganic fine particles excessively polish the specific portions, which can result in many fine scratches on the surface of the electrophotographic photosensitive member. When such fine scratches are generated in a large number in a portion of the surface of an electrophotographic photosensitive member and the scratches have a width of more than about 50 μm, output images have streak-shaped image defects such as white streaks.